电工技术学报  2024, Vol. 39 Issue (19): 6008-6017    DOI: 10.19595/j.cnki.1000-6753.tces.231445
电力电子 |
二次侧附加电容磁复位正激变换器电气性能分析及参数设计
刘树林, 庹汉宇, 张元昌
西安科技大学电气与控制工程学院 西安 710054
Electrical Performance Analysis and Parameter Design of the Secondary-Side Capacitor Magnetic Reset Forward Converter
Liu Shulin, Tuo Hanyu, Zhang Yuanchang
College of Electrical and Control Engineering Xi' an University of Science & Technology Xi' an 710054 China
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摘要 由于二次侧附加电容磁复位正激变换器具有结构简单等优点,因此有着较好的应用前景,但目前尚未见附加电容对电气性能影响及其设计方法的研究报道。为此,该文通过深入分析附加电容Cb对变换器工作模式和能量传输过程的影响,指出变换器存在四种组合工作模式,且励磁电感断续导通模式(DCM)/正激电感连续导通模式(CCM)最佳。Cb不仅能将励磁能量传输到负载,还可调节开关管电压应力,在负载不太大时实现续流二极管零电流关断(ZCS)和开关管低电压导通。通过分析Cb对变换器电气性能的影响,指出开关管电压应力随Cb增大而降低,开关管低电压导通性能随Cb和正激电感的减小而提升,并提出了一种确保变换器工作于最佳模式且可最大程度提升电气性能的参数设计方法。实例和实验结果验证了理论分析的正确性和设计方法的可行性。
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关键词 正激变换器磁复位低电压导通零电流关断    
Abstract:Aiming at the problem that the unidirectional magnetization of the single-switch forward conversion topology will lead to the saturation of the transformer, a variety of magnetic reset measures have been proposed. These measures can be broadly categorized as primary side magnetic reset and secondary side magnetic reset. The primary side magnetic reset can only consume the excitation energy on the resistance or feed back to the input side, so that the excitation energy can not be fully utilized,therefore, it is not beneficial to improving the energy transmission efficiency of the converter.The secondary side magnetic reset can transfer the excitation energy to the load during the switch-off period. However, the dual-winding structure on the secondary side increases the volume of the transformer and complicates the winding process. Additionally, the secondary side of the transformer with additional LCD (representing inductor, capacitor, and diode, respectively) different combinations of the structure of the converter, although it has a certain performance advantage, but it also increases the complexity of the circuit, so that its application has been limited to some extent. In contrast, the secondary-side additional-capacitor magnetically reset forward converter has a simple structure, requiring only one capacitor to achieve magnetic reset and transfer excitation energy to the load. Moreover, it facilitates enhancements in multiple electrical performances, effectively improving the performance and efficiency of the converter. This simplicity and performance enhances the application prospects. However, currently, there has been no research report addressing the impact of the additional capacitor on electrical performance and its associated parameter design methods. Therefore, this paper conducts a thorough analysis of the influence of the additional capacitor Cb on the energy transfer process and electrical performance of the converter. Additionally, a parameter design method is proposed to fully exploit the electrical performance advantages of the converter.
There are four combinations of operating modes for the secondary additional capacitance magnetic reset forward converter, among which the optimal mode is when the excitation inductor Lm operates in discontinuous current mode (DCM), and the forward inductor L operates in continuous current mode (CCM). When the converter operates in this mode, it achieves zero-current turn-off for the freewheeling diode and low-voltage turn-on of the switch under light load conditions. This prevents issues associated with diode reverse recovery and reduces the conduction losses of the switch, thereby enhancing the efficiency and system reliability of the converter.
Analyzing the relationship between the additional capacitor and the voltage stress on the switch under the operation of the excitation inductor in CCM and DCM, respectively. Based on the principle of energy conservation (i.e., the excitation energy generated by the transformer equals the energy stored in the additional capacitor within one cycle), an expression for the relationship between the additional capacitor Cb and the voltage stress on the switch was derived. It was concluded that the voltage stress on the switch can be adjusted through the additional capacitor Cb, and as Cb increases, the voltage stress on the switch decreases.
Through a thorough analysis of the zero current switching (ZCS) characteristics of the freewheeling diode and the low-voltage turn-on of the switch, it was pointed out that achieving ZCS for the diode requires the excitation inductor to operate in DCM, and the discharge current of the additional capacitor needs to rise to equal the freewheeling current of the forward inductor. Achieving low-voltage turn-on of the switch requires ZCS for the diode and the voltage across the additional capacitor VCb to be less than the output voltage Vo. However, these conditions necessitate that the current in the forward inductor not be too large, implying that these performance characteristics are only viable under light load conditions.
Combining the conditions for achieving ZCS for the diode and low-voltage turn-on of the switch, a design approach for the additional capacitor and the forward inductor was proposed. This method ensures that the converter operates in the optimal combination mode and fully leverages the electrical performance advantages of the converter. Experimental results validated the correctness of the theoretical analysis and the feasibility of the proposed design method. The research in this paper indicates that the secondary-side additional-capacitor magnetically reset forward converter holds broad prospects for widespread application.
Key wordsForward converter    magnetic reset    low-voltage turn-on    zero current switching   
收稿日期: 2023-08-31     
PACS: TM46  
基金资助:国家自然科学基金资助项目(51777167, 51604217)
通讯作者: 刘树林 男,1964年生,博士,教授,博士生导师,研究方向为开关变换器的分析与设计及本质安全电路等。E-mail:lsigma@163.com   
作者简介: 庹汉宇 男,1998年生,硕士研究生,研究方向为开关变换器的分析与设计及本质安全电路。E-mail:814064606@qq.com
引用本文:   
刘树林, 庹汉宇, 张元昌. 二次侧附加电容磁复位正激变换器电气性能分析及参数设计[J]. 电工技术学报, 2024, 39(19): 6008-6017. Liu Shulin, Tuo Hanyu, Zhang Yuanchang. Electrical Performance Analysis and Parameter Design of the Secondary-Side Capacitor Magnetic Reset Forward Converter. Transactions of China Electrotechnical Society, 2024, 39(19): 6008-6017.
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